The Sensex at the Bombay Stock Exchange gained 120 points, or 0.6 percent, to 20,466, on improved corporate earnings and firm Asian markets, today. The Sensex had added 193 points at the day's high, and gained 80 points at the day's low. The Nifty at the National Stock Exchange added 42 points, or 0.7 percent, to 6,161.